@Harry ********
Your trip in February is separate from the trip you are going to take. If you received a tourist visa (and haven't entered Thailand with it yet, in other words, haven't used it), it's still valid and you can enter Thailand during the 90 days of which the visa is valid (90-day countdown starts the day it is issued to you).
If you enter Thailand before it expires, you'll be able to extend it another 30 days at immigration for 1,900฿.